This invention relates to laminated gear shaving tools.
A tool of this type is used for a finishing operation only, the gear to be finished having already been produced by some other method, and is a gear-like member usually with a large number of teeth and having channels formed down each tooth flank to provide cutting edges on the serrations left therebetween. As shown in FIG. 1 of the accompanying drawings, which is an isometric view of two teeth 10,12 of conventional prior art tool, formed from a solid blank, these channels 14 run down each flank of each tooth from crown to root to form serrations 16 therebetween, usually terminating in a drilled hole or slot 18 at the root of the tooth. An accepted method of producing the channels 14 is to progressively feed a slotting tool 20 to the required depth; while in some cases the tool 20 is moved in a straight line (so the depth d of the channel 14 is not constant) in others it follows the involute curve giving a constant depth.
It has been proposed in U.S. Pat. No. 2,119,298 (Simowski) to form a gear shaving tool by laminating a plurality of similarly formed toothed discs (which term is similarly used throughout this specification to include discs having a central aperture, i.e. of annular form), the flanks of the teeth being relieved from one or both side faces of the disc to form a land, the lateral edges of which are spaced inwardly from the sides of the disc and constitute cutting edges. Configurations of disc teeth to form both helical and spur gear shaving tools are described.
FIG. 2 of the accompanying drawings is a partial axial section through a prior art laminated gear shaving tool 22 of the above type fabricated from a series of annular discs 24 (edge reliefs omitted) which are assembled together on a body 26 and clamped together mechanically by bolts 28 co-operating with end plates 30,32 which are typically of different radial extent. An alignment pin or keyway not shown is provided in each individual disc 24 in order to ensure that the discs can be assembled in the correct alignment and to resist the forces which will be applied to the serrations during cutting.
There are certain techniques of gear shaving commonly referred to as `plunge` or `underpass` which require the serrations to be staggered with respect to each other around the tool periphery so that the cutting edges are not in line with each other in the plane of rotation of the tool. Such a requirement cannot be met by teeth formed in the manner described in the above U.S. Patent and it is an aim of the invention to provide this facility.